Knock knock. Who's there? Cow says.

This little gem works by pulling a classic bait (Review)-and-switch on the knock-knock format itself. We're all programmed to hear the setup and automatically ask the "[Name] who?" question, fully expecting a groan-worthy pun to follow. But instead of playing along, the punchline slams the brakes on the joke's rhythm. It treats your question with a hilarious, deadpan literalness, correcting you as if you genuinely forgot what sound a farm animal makes. The humor isn't in a clever pun, but in the delightful absurdity of breaking the established rules.

It’s a perfect example of an anti-joke, where the expected payoff is swapped for something completely mundane and unexpected. The joke relies on one of the first animal sounds we ever learn, which makes the simple, factual correction even funnier. By hijacking the predictable structure of the knock-knock joke with such childlike logic, it creates a moment of pure, silly surprise. It's less of a "ha-ha" clever joke and more of an "aha!" moment of appreciating simple, goofy wordplay.